The present invention relates in general to the repairing, installing or otherwise manipulating of tubular members, and in particular to a new and useful apparatus and method for radially expanding tubes.
When installing or repairing tubes, it is often advantageous to manipulate and shape the tubes or tubular members from within the tubes.
In nuclear-fueled vapor generators, a repair process is known whereby a tubular member is placed inside a steam generator tube and expanded near its end. A brazed joint is then made to sealably fix the tubular member within the steam generator tube. The previous method for accomplishing this was to use a hydraulic expander to expand the tubular member in the joint area prior to brazing. This process proved to be too slow and cumbersome thereby limiting the number of tubes which could be repaired in a given period of time. This was especially disadvantageous with regard to nuclear steam generators since the longer repair time resulted in an increase in nuclear radiation exposure for pesonnel making the repairs.
A method and apparatus for hydraulically expanding tubing is known from U.S. Pat. No. 4,195,390 to Amen. An expandable bladder is mounted between the caps connected to each other by a tie rod situated within the bladder. Hydraulic pressure is internally supplied to the bladder to expand the bladder and a surrounding tubular member. However, as noted above, hydraulic expansion is much too slow, particularly in a nuclear radiation environment. Furthermore, external pressure sources are required which add to the time necessary in operating the Amen device.
More rapid expansion techniques are known which utilize propellant or explosive charges. U.S. Pat. No. 3,287,947 to Frantz et al, for example, discloses a tube flaring technique utilizing an explosive charge to outwardly flare the end of a tube. U.S. Pat. No. 3,876,233 to Schmedding et al discloses an automatic pipe coupling device which uses a propellant for effecting a wedging action to move two parts with respect to each other.